Pneumatic control apparatus



Jan. 24, 1939.

A. E. ROY PNEUMATIC CONTROL APPARATUS Filed May 19, 1937 2 Sheets-Shget 1 INVENTOR. g/bE/f 7670 j BY 'flfl/ ATTORNEY.

Jan. 24, 1939.

A. E.'ROY

PNEUMATIC CONTROL APPARATUS Filed Ma 19, 1957 INVENTOR. 4 56/7 5 0 7 ATTORNEY.

2 Sheets-Sheet 2 Y in control valves of the general type illustrated.

Patented Jim. 24, 1939 mums-no CONTROL mana'rus Albert E. Roy, Los Angeles, assignor 'to Vacnum Power Brake Company, Los Angeles, Calif., a corporation of California Application May 19, 1931, Serial No. 143.411;

1 12Claims. (01. 303-54) This invention is a continuation in part of my copending. application Serial No. 748,272, flied.

October 15, 1934 and relates .to pneumatic controlapparatus and particularly to improvements therein for utilizing the intake manifold vacuum of an internal combustion engine to actuate the brakes of an automobile, truck, trailer, or the like vehicle.

Heretofore in apparatus related to this invention where vacuum-operated vehicle brakes were controlled by means of semi-automatic manually operated valves of the type where the applied braking force,is a variable value proportional only to the displacement of the valve control and substantially independentof the duration ofv such displacement, diaphragm valves have been usually employed for the automatic operation of certain of the essential control mechanisms thereof.

In the employment of diaphragms, and particularly as to continuous diaphragms supported at the edges and center which also serve as valves, certain disadvantages are encountered, such as fluttering, leakage, and sluggish response due apparently to the inertia and internal stresses necessarily developed upon flexure of such structures. Another possible reason for imperfect operation ofcontinuous diaphragms tive in operation when constructed in the form which also serve as valve elements may be 'due to their natural tendency to periodic fluctuations.

It has been found that control valves oi the diaphragm type are more satisfactory and posi- Another object of this invention is to provide an improved valve means for controlling vacuum actuated apparatus which is substantially free from leakage and mechanically adapted to re-v main substantially leak-proof over a long period of operation.

It is also an object of my invention to provide an improved method of operating pneumatic con-' trol valves whichin eflect provides an automatic metering or regulation of the amount of vacuum supplied to the brake apparatus.

Other objects, advantages and novel features v of my invention will become evident from the following description of a preferred form of my invention and from the accompanying drawings in which: I a V Fig. 1 is a. diagrammatic partial perspective of the general arrangement of an apparatus embodying my invention; Fig. 2 is a longitudinal cross-section of the control valve of Fig. 1 taken along a vertical plane; Fig. 3 is a cross-section of said control valve taken on line 3-3 of Fig.

2; Fig. 4 is a fragmentary side elevation partly of a hand-controlled valve taken on line 5-5 of 6 'Fig. 4 with the diaphragm shown in an open sponding to Fig. 1, but showing a modified form of linkage and valve mounting.

Referring to the drawings and particularly to Fig. 1, the numeral Ill designates a control maype attached-to any suitable structural member of the vehicle chassis such as H The numeral ll designates a booster mechanism which may be of conventional design, and which is preftions; and Fig. 8 is a partial perspective corre- 50 valve in cross-section in Figs. 2 and 3 which erably rigidly attached to another suitable structural member ll of the vehicle chassis as illustrated in my copending application Serial No. 748,272. .A rod l2 extendingfrom the diaphragm of the booster unit-is connected to one end of a crank II which is carried on and keyed to a shaft ll which maybe rotatably supported in suitable bearings attached to the vehicle chassis not shown. The opposite'eri crank I3 is in turn connected to one 0 other crank l5,

the opposite endof which connected to a control rod l0 attachedtotlie stem ll ofthe control valve II. A foot pedal; li may be connected to an intermediate pivot point-of the crank I! as by 'means of the linkage.;i !1. --At the end portions I of, the shaft it are providedjdouble ended cranks ls The before-mentioned recesses in the housing comprise a main approximately cylindrical chamber 33 centrally located within thebody portion 30 and in communication through a central opening and a T connection 34 with the pipe 28, and a minor annular recess 35 concentric with said recess 33 and separated therefrom by a relatively thin annular shoulder 36. The minor annular recess 35 is'in communication through the lateral Opening 3| with the before-mentioned pipe 26. a l

A tubular-shaped guide member. is axially positioned in the center of the hemispherical cover 3| and serves to guide the controlvalve stem IT. A mushroom valve head 33, having an annular-shaped upturned valve seat 40, is carried on the inner end of the said valve stem I1 and occupies the forward central portion of the cylindrical chamber 33.

An annular flexible diaphragm 4| having a central opening 42 normally rests across andcloses the minor annular chamber 35 by making a substantially air-tight contact with the top surface of the annular dividing shoulder 36. The

said flexible diaphragm 4| is held in substantially air-tight contact with the valve body at its outer margin by means of an annular perforated flange 44 which bears upon the said outer phragm 4| in a closed position across the chamber 35 and upon the dividing shoulder 35 is positively applied to the inner circular portion 'munication through recess 31 with-the lateral 'ing 42 of the flexible diaphragm 4|.

of the before-mentioned flexible diaphragm by a helical spring 45 acting against a rigid annular metal washer, 46. The said metal washer 45 carries a downturned edge 46. which flts over the inner edge of the annular diaphragin and serves to define the previously-mentioned open- A second helical'spring 45' surrounds the valve stem guide and bears on the upper face of mushroom valve 33 adjacent its central portion and inside of washer 46 so as to normally urge'the valve away from hemispherical cover 3| and out of contact with diaphragm 4|.

The valve mechanism is thus normally divided into three.sea1ed chambers, namely; the outer chamber 43, deflned by the forward portion of the control valve under the hemispherical cover 3|, minor annular chamber 35 which is in compipe 25, and the centrally positioned major cy- -lindrical chamber 33 which is in communica tion through the r connection 34 with pipe 28.

The outer chamber 33 is maintained in communication with the atmosphere at all times by means of a plurality of vent holes or ports 48 which extend radially through the flange 44 and the adjacent portion of the'valve body as best shcwninl'ig. 3. Aflnemesh screen is pro;

vided between the flange and the adjacent body portion to prevent the entrance of dirt through the holes 38 with the air passing into the chamber 43.

The operation of the apparatus illustrated in Figs. 1, 2, and 3 is as follows:

When the elements of the apparatus are in the positions shown in Figs. 1 and 2, the brakes are in their normal or released position and the internal parts of the valve structure are in the positions shown inFig. 2,- that is, the flexible annular valve or diaphragm 4| is seated upon the annular shoulder 36 and closes the minor annular chamber 35, and is held in this position by the combined forced the spring 45 and the diil'erential pressure between the chamber 43 which is at atmospheric pressure and chamber 35 which isat sub-atmospheric pressure by reason ofits communication through pipe 25 with the engine intake manifold 21. The seat 43 of the mushroom valve 39 is clear of the annular flexible diaphragm 4| making a passageway therebetween, from the chamber 33 through the central opening 42 to the chamber 43. Air at atmospheric pressure from chamber 43 thus has access to chamber 33 andthence by way of the T connection 34 and pipe 23 to the booster unit Under this condition, both sides of the power diaphragm in the booster unit are at atmospheric pressure'and no force is applied to the braking mechanism through rod l2.

When pressure is applied to the foot pedal Hi, the resultant forward motion of the rod l3. causes the leverl5 to rotate momentarily in a counterclockwise direction about the upper end connection of crank l3, which in turh results in a momentary outward motion of the rod I3 and the attached valve stem I! of the control valve ID. This motion causes the mushroomvalve 33 to be moved into contact along its seat 40 with the flexible diaphragm 4| and upon suiiicient movement to lift said flexible diaphragm 4| against the force of spring 45 and the vacuum in chamber- 35 ofi of the annular shoulder 35. This results in both closing off communication between chambers 43 and 33 and-opening the passageway over the top of the annular shoulder 36 between chambers 35 and 33 whereupon the chamber in the booster unit II is put into communication with the sub-atmospheric pressure in the engine intakemanifold 21 by way of pipe 28, connection 34, chamber 33, chamber 35, and pipe 25. This results in a momentary reduction of pressure in the power chamber of the booster unit resulting in tension in the rod |2 which in turn causes a counter-clockwise rotational movement of the double ended crank l3 and cranks- 20 and 2| upon the shaft (H. The said counterclockwise rotational movement ofthe double the control valve l0 allowing the reseating of the flexible diaphragm 4| upon the shoulder 33.

This reseating of the flexible diaphragm 4| upon the shoulder 33 cuts of! further communication booster unit Howeven-thc valverod |l does 15 not move inwardly enough to cause valve 38 to disconnect from diaphragm 4!.

It is thus apparent that for any given depression of the foot pedal l8 resulting in a displacement of the valve mechanism in Ill that a counter-acting or restoring movement of the same valve mechanism is effected by the resultant motion of rod 12 of the booster unit 'll acting through cranks i3 and I5. This results in the application of pressure to the'braking mechanism which is proportional only to the deflection or displacement of the brake pedal l8. Overthence through pipe 28 to the booster unit ll braking by continued pressure upon the brake pedal isthus obviated.

Upon release of pressure from the brake pedal l8 subsequent to the process of applying the brakes as described hereinabove, themushroom valve 39 will be relieved of the force acting through the rods I9 and I6 and the valve stem 11, tending to hold it in contact with the flexible diaphragm 4|, and it will move inward by reason of the differential pressure between the chamber 43 and chamber 33 and spring45' until it is again unseated at 48 from the inner surface of the annular flexible diaphragm 4 las shown in Fig. 2, resulting in the opening of the passageway from chamber 43 through the central opening 42 ofthe diaphragm and around the raisedseat 48 of the mushroom valve 38 into the chamber 33. Air at atmospheric pressure is thus enabled to flow through the valve into chamber 33 and resulting in a reduction of force applied through rod I2 and through the before-described-associated linkages to the braking mechanism. This reduction of force results in a counter-acting reduction of the braking force is' thus obviously also proportional to the backward or restoring motion of the brake pedal l8.

Should the vacuum source fail for any reason, such as breakage of the line 25 or stalling of the engine, the brakes can be directly mechanically.

operated by applying sufficient pressure upon the pedal l8. This results in initial outward move: ment of the valve stem I! to the limit of its motion within the valve housing and from that point on, the force applied to the brake pedal I8 is transmitted directly throughthe rod l8, thence through the lower portion of the crank I! to the upper end of crank l3 without aid from the booster unit II. The forcethus applied tothe upper end of crank 13 is transmitted through the shaft i4, the-double ended cranks2ll and 2| and through the brake 'pull rods 22-25 as is usual. up

. Referring now to Fig. 4 which is a modified general arrangement of the apparatus incorporating a relay control valve and which is particularly adapted to installation on a trailer, 58 is a hand-operated control valve having a vacuum gage 5|. 52 is a vacuum-operated relay control valve, 53 a vacuum storage tank, 54 is a conventional type of'vacuum booster unit such as'shown at It in Fig. l, and I5 is a fragmentary view of an engine intake manifold. The vacuum booster unit 54, which is a typical installation for each wheel of the trailer, contains an internal flexiblediaphragm to which. is attachedithe brake pull 1 rod 55 which is in turn pivotally attached to the end of the brake mechanism actuating crank of'the brake drum 58. The said booster unit 54 is connected to therelay control valve 52 by way of pipes and II and branch pipe 82. Other branch pipes 83, 54, and 55 serve to make con-.

nection from the relay valve 52 to the other booster units, each of which actuatesthe braking mechanism for one of the severaiwheels of the trailer vehicle.

. The relay valve 52 is connected by way of pipe.

to the vacuum storage tank 53, and is also connected to the hand-operated control valve 50 byway of pipes 51, 68 and the flexible coupling 59. The vacuum storage tank 53 is connected tol the engine manifold 55, by way of the flexible pipe II, and flexible coupling-10.

The hand-operated control valve 58 may be conveniently supportedwithin reach of the op'erator, inside of the driver's compartment of the towing vehicle upon a suitable structural member 15. The vacuum storage tank 53, relay 'valve 52, 1

and booster. unit 54 with its'x'associated braking mechanism, together withtheiconnecting piping up to the flexible couplings 59 and Ill may be carried by the trailer vehicle, and when so arranged the couplings 69 and I0 constitute the flexible air connections between the towing vehicle and the trailing vehicle.

The hand-operated control valve 58 is shown in detail in cross-section in Fig. 5 and the main body portion thereof is substantially identical with that of the before-described control valve 'unit, ll shown in section in Fig. 2 The'flexible annular diaphragm 4i, mushroom valve 39, an-

nular washer 45, helical springs 45 and 45, together with the flange 44 and :the plurality of radial holes 48 are also substantially identical to those hereinbefore described in connection with Fig. 2 and, therefore, carry the same identifying numerals. I

The hemispherical cover" forthe body portion of the hand-operated control valve carries a valve stem guide I8 axially positioned and extending on the inside thereof, and on the outside a similar axially positioned cylindrical projection '18 about which is rotatably supported cam ring 88.

The lower face of the'cam ring 80 has a plane surface resting upon an annular ofiset bearing surface ii on the top central portions of the cover l1, As seen best in Fig. 6, the top of the cam ring 88 carries a pair of helical-shaped cam surfaces 82 and '83 each of which extends approximately 180 around the ring and terminates in stop lugs 34 at their raised ends, and recesses 85 at theirlower ends. It being found preferable to have the depth of said recesses approximately equal to the desired clearance between valve head 33 and diaphragm 4|, so that the valve head 39 is raised to contact diaphragm 4| almost immediately upon movement of the handle I in.

through the external cylindrical projection 18.

tubular in section for a portion of its lengthand is provided with a diametrally disposed longitudinally elongated slot 81 through which a crosswise positioned pin or cam-riding pin 88 extends.

[It will be noted that by having the opposite" cam surfaces 82 and that uponmovement of The outer end'portion of the valve stem. 86 is 65 The valve stem 88 of the mushroom valve 39 I extends through the valve-stem guide "and the cam ring 88, one end of the pin 88 tends to roll up one cam face, while the other end of the pin tends to roll down the opposite cam face. By this arrangement, the friction between the pin 88 and cam faces 82 and 83 is utilized to keep the cam ring in any fixed position and eliminate the necessity of separate friction devices therefor.

The upper extremity of the tubular portion of the stem 88 is externally threaded to receive a regulator knob 89 having an internally thread.- ed socket 98. A coil spring 9| is retained within the tubular end portion of the valve stem and is normally maintained under compression between the cam riding pin 88 and the ball 92 in the regulator knob socket 98.

The cylindrical projection I9 is slotted at 93 and 94 to receive the cam riding pin 88 and to allow only longitudinal motion hereof upon rotation of the cam ring 80. The extending portions of the cam riding pin 88 are urged against the upper cam surfaces 82 and 83 by the spring 9| which is under compression and at the same time.

urges the valve stem 88 and the seat 48 of the mushroom valve 39 upward with equal force against the inner marginal valve seat portion of the under surface of the annular flexible diaphragm 4I. bears against the diaphragm 4i may thus be adjusted by the regulator knob 89 and controlled at will by movement of the position of the cam ring 88.

The camring 88 is operated by a handle II8 which extends radially from an inverted cupshaped central hub portion 95, which encloses the cam ring and retains the cam riding pin 88. Said hub portion 95 is attached in a fixed relation to the cam ring 88 by means of setscrews 96 and 91, and the cam ring may be thus rotated by application of force to the handle H8. The

upper end of the valve stem 88 which carries the adjusting knob 89 extends through a central opening in the hub portion 95.

As described hereinbefore in connection with the foot valve of Fig. 2, the hand-operated concating gage 5| may be connected to the chamber.

33 by pipe 98, and serves to visually indicate the braking forcebeing applied through the valve.

Referring to Fig. 7 which illustrates the relay valve '52 in cross-sectional view, the lower body portion thereof is identical with the lower body portion of the control valve I8 as shown in Fig. 2.

The hemispherical cover 98 is generally simflar to that illustrated in Figs. 2 and 5 but instead of having a valve guide through thecentral portion thereof a pipe connection 99is substituted, from which thepipe 81 extends to the control valve- 58. 'Theannular flexible diaphragm 4|, the annular washer 46 and the mushroom valve 39 are all similar to those'same elements in Figs. 2 and 5 and, therefore, bear the same identifying numbers. The valve stem I88 extending upwardly from the mushroom valve 39 is shorter than the ones illustrated in the other types of valves and terminates in a threaded portion I8I within the enclosure of the hemispherical cover 98.

The force with which the valve 39 f 'crimp or hip 4I'.

plate H5 provided with flanges 44 and adapted to be rigidly held between cover 98 and body portion 34 of the valve mechanism. Theplate H5 preferably has a downwardly extending boss H6 at its center which is apertured to receive the valve stem I88. The upper face of the plate H5 is re-,

cess ed around the central aperture to accommoopening concentric with the central aperture of plate II 5 to accommodate valve stem portion I8I, and is secured by means of a nut I clampedbetween upper washer I83 and lower washer I84 which fits inthe'before-mentioned recess in plate H5. The diaphragm I82 thus divides the upper portion of the relay valve into two separate chambers illustrated at I II and H2.

A coil spring I88 is interposed between the washer I83 and the top of the cover 98. A helical spring I8! is interposed between the annular washer 48 and the underside of plate H5 which serves to retain the flexible diaphragm 4| in normal sealing contact with the shoulder 36.

Chamber III formed between the diaphragm normally divided into four chambers namely the uppermost chamber H2 communicating with the pipe 61 leading to the control valve, the intermediate chamber III communicating with the atmosphere through the vent holes 48 and thus remaining at atmospheric pressure, the annular minor chamber 35 in communication with the vacuum storage tank 53 through pipe 66 and the major central cylindrical chamber 33 in communication withv the-vacuum booster unit 54 through pipe 58. .trol valve 58 of Fig. 5-is normallydivided into three chambers, namely, chamber 43, which is in The flexible annular diaphragm 4| shown in Figs. 2, 5, and 7 may be composed of any suitable material such as rubber, duprene, or the like. It will be noted that in each instance I have shown the diaphragm as provided with a small annular By reason of this hip 4i, it is possible to securely clamp the outer margin of "the diaphragm and still allow free and adequate movement of the central portion of the dia-' phragm without stretching the same. As will be evident, this eliminates substantially all internal stresses yet gives plenty of flexibility without fluttering, and results. in a valve with a high degree of sensitiveness with a minimum amount of wear on'the parts.

The operation of the apparatus of Figs. 4-7 is as follows: I v Assuming that there is a sub-atmospheric pressure in the'tank 53 and that the brakes are released, the relay valve mechanism of Fig; '7 will be in the position shown therein, and the hand control valve mechanism of Fig. 5 will also be in a like position with .the flexible annular diaphragm seated upon the shoulder 38 and closing the annular chamber 35, and the mushroom valve 39 will be unseated from the under surface of said flexible diaphragm 4| and in an open position contrary to the position of those same elements as illustrated in Fig. 5. Upon turning the handle H8 and the attached cam ring 88 to raise the valve 39 against the under surface of the annular flexible diaphragm 4I the position of the elements as shown in Fig. 5 will obtain. This results in closing oh the main booster line 03 from the atmosphere and in opening a passageway between chambers 35 and 33 by raising the flexible diaphragm 4| oi! oi the dividing shoulder 30 and thus putting chamber H2 or the relay valve unit 52 in communication with the region of sub-atmospheric pressure in the intake manitold 55 and storage tank 53 by way of pipe 61, flexible coupling 69 and pipes 69 and I4.

It is to be noted that the force oi! the cam 80 is transmitted to the valve 39 through the coil spring '9I which deflects under compression so.

that it tends to yield under the combined opposing force of the helical spring 45 and the differential pressure between chambers 43 and 33. As the valve 39 in response to motion oi. the handle II and the cam ring 30 moves upward carrying with it the flexible diaphragm H, the differential pressure between chambers 43 and 33 is increased by reason of the communication thus established between the chamber 33 and the sub-atmospheric pressure in chamber 35. This increase in difierential pressure acting upon the flexible diaphragm H and upon the mushroom valve 39 increases the loading and hence the deflection oi the coil spring 9|. When the pressure diflerential has thus be come sufllciently great, the deflection of the coil spring 9I will be sumcient to allow the flexible diaphragm H to reseat upon the annular should'er 36 and thus to cut oilf further reduction of pressure in chamber 33.

This variation in the degree of vacuum in the chamber 33 as controlled by the handle 0 inbefore will result in a deflection of the dia-- phragm I02 causing the valve stem I00 and the attached mushroom valve 39 to follow exactly thosecorresponding movements of the valve 39 in the before-described control valve 50. The valve mechanism of the relay valve thus operates in the same manner as the same valve mechanism in the control units illustrated in Figs. 2 and 5, to' vary the degree of vacuum in the chamber 33. Since the chamber 33 is in communication with the booster units 54, through the pipes 50-65 the said variation in pressure results in a corresponding braking action upon the various braking mechanisms of the vehicle wheels.

Thus the braking force applied to the vehicle may be remotely controlled by means of the hand-operated control valve 50 through the action of the relay valve 52, and the magnitude of such resultant braking force is proportional only to the angular displacement of the control lever 0, which may be set and allowed to remain in any given position without increasing the braking force beyond the value corresponding to such displacement. The maximum braking force applied to the booster units for. any given angular displacement of the control handle H0 is adjustable by .the threaded knob 39 which acts tain- 'crease or decrease the initial compressive force acting upon the coil spring 9|.

If desired, the relay valve 52 may be omitted and'the main booster line 00, may be connected directly to the hand control valve through line 03. This omission of the relay valve may be desirable in some cases where the braking mechanisms to be operated are on the main vehicle in which the control valve 50 is installed, however, in the case of the installation upon a trailer vehicle, the provision for a relay valve unit as illus-' trated in Fig. 4 may be desirable.

From the foregoing, it will be seen that both the foot valve installation oifFig. 2 and the hand valve structure of Fig. 5 are automatically compensating, and that the pressure applied to the brakes through the booster is always proportional to the displacement of the power member, whether it be the foot pedal I8 or handle IIO.

In Fig.8, I have illustrated a modified 'form of mounting for the foot valve of Fig. 2 which partakes of the feature shown in both Fig. 1 and Fig.

5. Giving the same numerals to like parts found in Fig. 1, I have a brake pedal I8, brake rod I9, crank I3, shaft I4, booster II, booster rod I2, foot valve I0 with valve stem 'II, bracket I0, and pipe connections 26 and 28 leading from the valve I0. In this instance, however, the intermediate crank I5 is eliminated and the rod I9 is provided with a slot I20; pin connected to the upper arm of crank I3, and also connected by a spring I2I to valve stem II. The spring I2I functions similarly to spring 9| in the hand valve 50 to yieldably pull valve stern I1 and valve 39 outwardly against the force of springs 45 and 45 and the differential pressures in the valve. When sub-atmospheric Pressure has been established in chambers 33 to the desired point in response to a given displacement ofthe brake pedal I8, the spring I2I yields and the valve diaphragm 4| reseats on its shoulder 36, thus giving a compensated braking force. If the valve does not function, continued movement of the brake pedal causes the end of the slot I20 to engage crank I3 and operate the brakes directly.

Itis to be understood that the foregoing is merely illustrative of preferred embodiments of my invention, and that numerous variations apparent to those skilled in the art may be made in the forms shown without departing from the invention as defined by the appended claims.

I claim as my invention:

1. In a vacuum-operated braking system for vehicles, a control valve comprising; a housing consisting of a recessed body portion and a cover for said recessed body portion; an annular shoulder in said recessed body portion defining an outer annular chamber and a coaxial centralI communication with the atmosphere; and means to move said valve and said flexible diaphragm whereby. communication mail. be alternately and said annular chamber and between said central chamber and said atmospheric chamber.

2. In a vacuum-operated braking system for vehicles, a control valve comprising: a housing consisting oi. a recessed body portion and a cover ifor said recessed body portion;

shoulder in said recessed body defining an outer annular chamber and a coaxial central chamber;

v established thereby between said central chamber an annular chamber; a circular valve head insaid central an annular-shaped flexible diaphragm fixed at its outer edge and normally covering said annular chamber and a portion of said central chamber;

an annular ring in contact with the inner periphery of said flexible diaphragm; a spring seating upon said ring and "urging said flexible diaphragm toward contact with said annular shoulder; a circular valve head in said central chambercovering the central opening in said annularshaped flexible diaphragm, said flexible diaphragm and said circular valve forming a partition in the housing between said body portion and said cover, said partition defining an additional chamber under said cover in communication with the atmosphere; and means to'move said valve and said flexible diaphragm whereby communication may be alternately established thereby between saidcentral chamber and said annular chamber and between said central chamber and said atmospheric chamber.

3. In a vacuum-operated braking system for vehicles, a control valve comprising: a housing consisting of a recessed body portion and a cover for said recessed body portion; an annular shoulder in said recessed body defining an outer annular chamber and a coaxial central chamber;

a circular annular-shaped flexible diaphragm, having a concentric circular central opening, fixed at its outer edge and normally covering said annular chamber and a portion oi said central chamber covering the central opening in said annular-shaped flexible diaphragm, said flexible di- 'aphragm and said circular valve forming a partition in the housing between said body portion and said cover, said partition defining an additional chamberin communication with the atmosphere; and elastic means to move said circular valve and said flexible diaphragm whereby communication may be alternately established thereby between said central chamber and said annular chamber and between said central chamber and said atmospheric chamber.

4. Apparatus as set forth in claim 3 in which the elastic means to movesaid circular valve com: prises an expansible chamber in said housing adapted to receive air under variable pressure.

5. Apparatus as set forth in claim 3 in which the elastic means to move said circular valve comprises a spring and means to apply a variable force to said spring.

6. In a vacuum-operated braking system for vehicles, a control valve comprising; a housing consisting of a recessed bodyportion and a cover for said recessed body portion: an annular shoulder in said recessed body defining an outer annular chamber and a coaxial central chamber; a. circular annular-shaped flexible diaphragm,

having a concentric circular central opening,-

fixed at its outer edge between said body and cover and normally cpvering said annular chamber and a portion of said central chamber; a circular valve head in said-'centralchamber covering the central opening in said annular-shaped'fiexible diaphragm, said flexible diaphragm and said circular valve forming a partition in the-housing between said body portion and said cover, said partition defining an additional chamber in communication with the atmosphere; a. valve stem attached at one end to said circular valve; a spring at the opposite end of said valve stem; and means to apply a variable force through said spring to said valve stem tomove said circular valve whereby communication may be aland cover and normally covering said annularchamber and a portion of said central chamber; a circular valve head in said central chamber covering the .central opening in said annularshaped flexible diaphragm, said flexible dia-' phragm and said circular valve i'ormng a partition in the housing between said body portion and said cover, said partition defining an additional chamber in communication with the atmosphere; a valve stem attached at its end to said circular valve;- a spring at the opposite end of said valve stem; and cam means to apply a variableforce through said spring to said valve stem to move said circular valve whereby communication may be alternately established thereby between said central chamber and said annular chamber and between said central chamber and said atmospheric chamber.

8. In a vacuum-operated braking system for vehicles, a control valve comprising: a housing consisting of a recessed body portion and a cover for said recessed body portion; an annular shoulder in said recessed body defining an outer annuannular-shaped flexible diaphragm fixed at its outer edge between said body portion and said cover and normally covering said annular chamber and a portion of said central chamber; an annular metal ring in contact with the inner lar chamber and a coaxial central chamber; an i periphery of the said flexible diaphragm; a

spring seating upon said metal ring and urging said flexible diaphragm toward contact with said annular shoulder; a circular valve head in said central chamber covering the central opening in said annular-shaped flexible diaphragm, said flexible diaphragm and said circular valve forming a partition in the housing between said body portion and said cover, said partition defining an additional chamber under said cover in communication with the atmosphere; 9. second'spring attached to said circular valve; means to apply I a variable force to said circular valve through said second spring to move said valve and said flexible diaphragm whereby communication may be established thereby from said central chamber alternately to said annular chamber and to said atmospheric chamber.

9. In a vacuum-operated braking system for 'vehicleaa control valve comprising: ahousing consisting of a recessed body portion and a cover for said recessed body portion; an annular shoulder in saidreces'sed body portion defining an outer annular chamber and a coaxial central chamber; an annular-shaped flexible diaphragm fixed at its outer edge and normally covering said annular chamber and a portion of said central chamher; a circular valve. head in said central chamber covering the central openingin said annularshaped flexible diaphragm}; 'said flexible diaphragm and said circular valve forming a partition in the housing between said body portion and said:- cover,said partition defining an additional chamber in communication with theatmosphere; a valve stem attached at one end to said circular valve; a tubular section at the opposite end of the valve stem; a coil spring in said tubular section; means to apply a variable force to said valve stem through said coil spring to move said circular valve whereby communication may be alternately established thereby between said central chamber and said annular chamber and between said central chamber and said atmospheric chamber. v

10. In a vacuum-operated braking system for vehicles, a control valve comprising: a housing consisting of a recessed body portion and a cover for said recessed body portion; an annular shoul der in said recessed bodyportioni defining an outer annular chamber and a coaxial central chamber: an annular-shaped flexible diaphragm fixed at its outer edge between said body and cover and normally covering said annular chamher and a portion of said central chamber;- a

circular valve head in said central chamber covering the central opening in said annular-shaped flexible diaphragm, said flexibledlaphragm and said circular valve forming a partition in the housing between said body portion and said cover, said partition defining an additional chamber in communication with the atmosphere; a valve stem/attached at its one end to said circular valve; a tubular section at the opposite end of said valve :stem; a coil spring in said tubular section; adjustable means to apply an initial compressive force to said coil spring; separate means to apply a variable force to said valve stem through said coil spring to move said circular valve whereby communication may be alternately established thereby between said centralchamher and said annular chamber and between said central chamber and said atmospheric chamber.

and said atmospheric chamber.

11. In a vacuum-operated braking system for vehicles, a control valve comprising: a housing consisting of a, recessed body portion and a cover therefor; an annular shoulder in said body portion defining an outer annular chamber and a coaxial central chamber; an annular-shaped flexible diaphragm fixedly supported in said housing across said chamb'ers,.said diaphragm being provided with an annular hip adjacent its outer edge a valve head disposed belowsaid diaphragm with its stem extending therethrough, said diaphragm and said head together forming a' partition in the housing, said partition defining an additional chamber in said housing and in communication with the atmosphere; and means to move said valve head and diaphragm toalternately establish communication between said central chamber and said annular chamber and behousing and in communication with the atmosphere, and means to move said valve head and diaphragm to alternately establish communication between said central chamber and said annular chamber and between said central chamber ALBERT E. ROY. 

